Web maps are kind of images and creating images are always a bottleneck for the computers. Web mapping clients, such as Google Maps, MS Virtual Earth, Google Earth and OpenLayers, are consuming WMS (Web Map Service) data for every user. The same image can be produced for every request, which is quite unnecessary. Caches can be called proxies between map clients and WMS servers to cache tiles not to reproduce every image again and again.

PHPGeoTiles is another caching tool for web mapping applications written in PHP under BSD License. There are other caching tools such as TileCache (python) and GeoWebCache (java) if you prefer other languages.

PHPGeoTiles is storing map tiles on your disk or Google App Engine's database, "BigTable". The difference of PHPGeoTiles is using Google App Engine to store tiles addition to disk storage, thus there is also a small portion of python codes to store tiles on BigTable addition to PHP codes.